I. Field of the Invention
This application pertains to a tool for use in the construction trades. More particularly, this application pertains to a tool for use in applying drywall compound to a drywall joint.
II. Background of the Invention
In the construction trades, drywall (also called sheet rock or blue board) is commonly used to finish interior walls as an economical alternative to lathe and plaster interior walls. In drywall installation, a plurality of dry wall sheets (commonly 4'.times.8') are fastened to wall studs and ceiling joints by screws or nails. Contiguous drywall sheets define a joint which must be filled before the drywall can receive a finished coat of paint or wall paper.
Basically, there are three types of drywall joints. The first is a joint formed by contiguous sheets of drywall which lie in the same plane. The second is an exterior corner joint formed by two sheets of drywall abutted together in a generally convex configuration. The third is an interior corner joint formed by two sheets of drywall being joined in a generally concave configuration. In finishing all of the above joints, a drywall compound is used. Drywall compound is a putty-like material which is forced into the joint and feathered out onto the drywall sheets. After the compound drys, it is either sanded or sponge wiped until it is smoothed into the sheets and the joint is completely covered. Frequently, due to shrinkage of the drywall compound, several coats of drywall compound are required for finishing each joint.
In finishing a flat joint, the drywall compound is applied with a wide blade putty knife which, as it moves along the length of the joint, urges drywall compound into the joint and smooths out the drywall compound into the surfaces of the contiguous drywall sheets. A common flat joint includes a first layer of drywall compound, a layer of drywall tape and one or more successive layers of drywall compound.
In finishing exterior corners, a metal bead edge is commonly fastened to the corner and drywall compound is applied to both sides of the bead edge by a wide bladed putty knife which smooths out the surface of the compound between the edge of the metal bead and a flat surface of the drywall sheet.
Particular problems arise when finishing an interior corner. Such a joint is commonly finished by applying a first coat of drywall compound and then a layer of drywall tape followed by one or more successive layers of drywall compound.
In the trade, it is difficult to provide a nice, smooth application of drywall compound on an interior joint. In conventional construction, interior walls meet at a 90.degree. angle. For such 90.degree. joints, a special tool is available which includes two rigid blades joined at a 90.degree. angle. This tool is urged into the 90.degree. corner defined by the drywall sheets and smooths out the drywall compound and drywall tape until it assumes the desired 90.degree. angle finishing the joint.
Building designs frequently deviate from the standard 90.degree. interior corner. The design of the building may call for interior corners having angles significantly greater or less than 90.degree.. In such circumstances, the conventional interior corner tool cannot be used. Instead, the prior art of drywall finishing required the tradesmen to use a long bladed putty knife to apply the drywall compound and the drywall tape. This required two passes for each application. In each pass, one end of the blade would be positioned within the corner defined by the drywall sheets and the blade would be drawn along the length of the joint to smooth out the compound on one of the drywall sheets. The next pass required placing the end of the blade in the edge of the joint and smoothing out the compound on the other drywall sheet. This two-step process frequently resulted in a wavy line being formed down the length of the joint. This wavy line is attributable to the fact that the tradesman does not always draw the putty knife in a precisely straight line. The existence of this line required time consuming efforts to smooth out the line or otherwise make sure that the line was not formed. However, this is time consuming and expensive. It has long been recognized that it would be desirable to have a tool which could be used to apply compound to the interior joints with a single application and avoid the need to take time-consuming efforts to smooth out an interior joint.